Fix links

README.md

@@ -16,6 +16,22 @@ Read Online:
 * [**Kindle MOBI**](http://dev.stephendiehl.com/hask/tutorial.mobi)
 * [**Example Code**](https://github.com/sdiehl/wiwinwlh/tree/master/src)
 
+If you'd like a physical copy of the text you can either print it out for
+yourself (see Printable PDF) or purchase one from a publisher. The price is
+at-cost since the book is open source and free.
+
+* [Blurb Publisher](https://www.blurb.co.uk/b/9958091-what-i-wish-i-knew-when-learning-haskell)
+
+The current published version is:
+
+```
+Date: February 16, 2910
+Git: d429c2e21b9636cffa27a8d4f063644b8bcecf1a
+```
+
+Source Code
+-----------
+
 Chapter Code Examples:
 
 * [01-basics/            ](https://github.com/sdiehl/wiwinwlh/tree/master/src/01-basics/)

tutorial.md

@@ -2272,7 +2272,7 @@ list of integral values, each element multiplied by two.
 
 ```haskell
 λ: [2*x | x <- [1,2,3,4,5]]
---        ^^^^^^^^^^^^^^^^^
+--        ^^^^^^^^^^^^^^^^
 --            Generator
 [2,4,6,8,10]
 ```
@@ -6833,7 +6833,7 @@ data Bool = True | False
 
 isNotJust :: Maybe a -> Bool
 isNotJust (Just x) = True
-isNotJust (Just x) = False
+isNotJust Nothing = False
 
 isJust :: Maybe a -> Bool
 isJust (Just x) = True